Google Guava

Google Guava

• 1.
  Google Guava Scott Leberknight
• 2.
  "Guava is theopen-sourced version of Google's core Java libraries: the core utilities that Googlers use every day in their code."
• 3.
  "Guava has beenbattle-tested in production at Google"
• 4.
  "Guava has staggeringnumbers of unit tests: as of July 2012, the guava-tests package includes over 286,000 individual test cases." WAT???
• 5.
  "Guava is underactive development and has a strong, vocal, and involved user base."
• 6.
  collections concurrency primitives reflection comparison I/o math strings hashing caching in-memory pub/sub net/http
• 7.
  Examples...
• 8.
  preconditions checkArgument(age >= drinkingAge, "agemust be greater than %s", drinkingAge); checkNotNull(input, "input cannot be null");
• 9.
  "Null sucks" -Doug Lea
• 10.
  avoiding nulls Optional<String> value= Optional.fromNullable(str); if (value.isPresent()) { // ... }
• 11.
  joining strings List<String> fruits= Arrays.asList("apple", null, "orange", null, null, "guava"); String joined = Joiner.on(", ").skipNulls().join(fruits); // "apple, orange, guava" List<String> fruits = Arrays.asList("apple", null, "orange", null, null, "guava"); String joined = Joiner.on(", ).useForNull("banana").join(fruits); // "apple, banana, orange, banana, banana, guava"
• 12.
  splitting strings String input= ",, ,apple, orange ,,, banana,, ,guava, ,,"; Iterable<String> split = Splitter.on(',').omitEmptyStrings().trimResults().split(input); // [ "apple", "orange", "banana", "guava" ]
• 13.
  CharMatcher CharMatcher matcher = CharMatcher.DIGIT.or(inRange('a','z').or(inRange('A', 'Z'))); if (matcher.matchesAllOf("this1will2match3")) { // ... } String input = " secret passcode "; String result = CharMatcher.WHITESPACE.trimFrom(input);
• 14.
  Objects Objects.equal Objects.toStringHelper compareTo() via ComparisonChain Ordering
• 15.
  Multiset Track frequencies of elements,e.g. "word counting" Iterable<String> words = Splitter.on(' ').split(document); Multiset<String> wordCounts = HashMultiset.create(words); for (Multiset.Entry<String> entry : wordCounts.entrySet()) { String word = entry.getElement(); int count = counts.count(element); System.out.printf("%s appears %d timesn", word, count); }
• 16.
  Map<String, List<String>> Tired ofthis?
• 18.
  Multimap Multimap<String, String> mm= ArrayListMultimap.create(); Collection<String> smiths = mm.get("Smith"); // empty collection (never null) mm.put("Smith", "John"); mm.put("Smith", "Alice"); mm.put("Smith", "Diane"); smiths = mm.get("Smith"); // [ "John", "Alice", "Diane" ]
• 19.
  Sets Set<String> set1 =Sets.newHashSet("apple", "orange", "guava"); Set<String> set2 = Sets.newHashSet("guava", "clementine"); Sets.SetView<String> diff1to2 = Sets.difference(set1, set2); // "apple", "orange" Sets.SetView<String> diff2to1 = Sets.difference(set2, set1); // "clementine"
• 20.
  Table Table<R, C, V>
• 21.
  Ranges & Domains Range<Integer> range= Range.openClosed(0, 10); ContiguousSet<Integer> contiguousSet = ContiguousSet.create(range, DiscreteDomain.integers()); ImmutableList<Integer> numbers = contiguousSet.asList(); // [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ]
• 22.
  FP in Guava FluentIterable<Integer>squaresOfEvens = FluentIterable.from(numbers) .filter(new Predicate<Integer>() { @Override public boolean apply(@Nullable Integer input) { checkNotNull(input, "nulls are not allowed here!"); return input % 2 == 0; } }) .transform(new Function<Integer, Integer>() { @Nullable @Override public Integer apply(@Nullable Integer input) { checkNotNull(input, "nulls are not allowed here!"); return input * input; } }); // [ 4, 16, 36, 64, 100 ] WAT?
• 23.
  Until Java 8... List<Integer>squaresOfEvens = Lists.newArrayList(); for (Integer number : numbers) { if (number % 2 == 0) { squaresOfEvens.add(number * number); } } // [ 4, 16, 36, 64, 100 ]
• 24.
  "Excessive use ofGuava's functional programming idioms can lead to verbose, confusing, unreadable, and inefficient code.These are by far the most easily (and most commonly) abused parts of Guava, and when you go to preposterous lengths to make your code "a one-liner," the Guava team weeps."
• 25.
  ListenableFuture // setup... ExecutorService delegate= Executors.newFixedThreadPool(MAX_THREADS); ListeningExecutorService executorService = MoreExecutors.listeningDecorator(delegate); // submit tasks... ListenableFuture<WorkResult> future = executorService.submit(worker); Futures.addCallback(future, new FutureCallback<WorkResult>() { @Override public void onSuccess(WorkResult result) { // do something after success... } @Override public void onFailure(Throwable t) { // handle error... } }, executorService););
• 26.
  @Beta "...subject to change..."
• 27.
  "Guava deprecates, andyes, deletes unwanted features over time. It is important to us that when you see a feature in the Javadocs, it represents the Guava team's best work, and not a feature that in retrospect was a bad idea."
• 28.
  Get some Guava!
• 29.
  References https://code.google.com/p/guava-libraries/ https://code.google.com/p/guava-libraries/wiki/GuavaExplained https://code.google.com/p/guava-libraries/downloads/list http://docs.guava-libraries.googlecode.com/git-history/release/javadoc/ index.html http://www.tfnico.com/presentations/google-guava http://codingjunkie.net/tag/guava/
• 30.
  Photo Attributions * thisone is iStockPhoto (paid) --> http://www.morguefile.com/archive/display/138854 http://www.flickr.com/photos/hermansaksono/4297175782/ http://commons.wikimedia.org/wiki/File:Guava_ID.jpg http://www.flickr.com/photos/88845568@N00/2076930689/ http://www.flickr.com/photos/mohannad_khatib/6352720649/
• 31.
  https://github.com/sleberknight/google-guava-samples Sample code available at:
• 32.
  My Info scott dotleberknight at nearinfinity dot com twitter.com/sleberknight www.sleberknight.com/blog www.nearinfinity.com/blogs/scott_leberknight/all/ scott dot leberknight at gmail dot com